Fireplace Damper vs Flue: What’s the Difference?

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A fireplace damper and flue are two essential aspects of a fireplace - but what's the difference? Find out here!

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There are many essential aspects of a fireplace. The damper and flue are two of the most important yet often misunderstood. The fireplace damper vs. flue debate has been around for years.

One crucial thing you always have to remember is to perform proper fireplace and chimney maintenance for the safety of your home.

The damper is located at the top of the fireplace, just below the mantel. The flue is located further down, near the bottom of the firebox. The damper’s primary purpose is to control airflow into and out of the fireplace. On the other hand, the flue’s primary purpose is to vent smoke and gases up and out of the fireplace.

Keeping track of all the different components of the fireplace and chimney can be confusing. Luckily, we are here to help!

What’s the Difference Between a chimney flue and a fireplace Damper?

What Is a Fireplace Flue?

A fireplace flue is a passage in a chimney for hot gases and smoke from a fire. The word “flue” comes from the Latin word “fumus,” meaning “smoke.” Flues are typically lined with heat-resistant materials such as clay tile, firebrick, or metal.

How Does a Fireplace Flue Work?

A fireplace flue resembles a ductwork and brick chimney. It functions by taking the exhaust gases and debris from the fireplace and going up to the chimney and outside. Therefore, its main objective is to direct combustion up and out of the chimney. 

The stack effect is what makes superheaters work. The temperature difference between the indoor and outdoor parts creates a stack effect that helps the superheater.

This happens because the chimney is taller than all flues and vents combined. The exhaust gases, lighter in weight than the cold outdoor air, flow up through the flue and vent outside.

In addition to this, some heat is lost during this process, and you can make modifications in or above the firebox to minimize it. The flue enables the entrance of fresh air and fire oxygenation.

Do All Chimneys Have a Flue?

No, not all chimneys have a flue. Some have only one duct or passage, while others may have multiple passages. The term “flue” is most often used to refer to the passage that carries exhaust gases and smoke from the fire up and out of the chimney.

A flue is necessary for any gas, wood-burning appliance, or fireplace. It lets the smoke, carbon monoxide, and waste gases out of your home without being trapped inside. It might be located in a chimney or as little as a simple pipe. But it’s the duct through which smoke and waste gases, such as carbon monoxide, evacuate the house.

The duct should be the correct size to match the capacity of your fire system and free of obstructions for optimum airflow. Ensure you line it properly to prevent hazardous fumes from getting into the house.

You need a flue for a wood-burning fire since it allows the chimney to function correctly. If you’ve recently purchased a home, have your chimney inspected by a professional to ensure your flue and chimney system is safe.

If you’ve owned your house for a while and have used your system for years but haven’t had it inspected in the last year, you should schedule this appointment right away.

How to Tell if My Flue is Fully Open?

The best way to tell if your flue is fully open is to look up inside the firebox while someone lights a match and hold it near the edge of the opening. If you see any flames drawn up into the chimney, your flue is open and functioning correctly. If not, you may need to have it inspected by a professional.

Tips on How to Test if the Flue is Open/Blocked

Using Paper

Another way to test if your flue is fully open is by using paper. Light the paper on fire and hold it close to the damper opening. If the paper gets sucked into the fireplace, your flue is open. However, if the paper falls, your flue might be obstructed and needs to be cleaned.

Damper Position

If you know how the damper controls work on your fireplace, you can check to see the position of the damper without having to go up and look in the chimney.

If you can’t turn the handle further, the damper may already be open. When handles are pulled towards you, the damper will be closed.

You can operate the throat dampers with a lever to switch to the right or left. Pushing the lever to the left will close the damper, whereas moving it to the right will open it.

Types of Fireplace Flue

Here are the different types of chimney flue:

  • Clay chimney flue – These are the most common type of flue made from clay fired in a kiln. The average lifespan of a clay chimney flue is about 20 to 30 years.
  • Metal chimney flue – Metal chimney flues are either galvanized steel or stainless steel and can last 50 to 100 years.
  • Cast-in-place concrete chimney flue – These types of flues are made by pouring concrete into place around a metal form. They’re typically used in commercial buildings but can also be found in some homes. The average lifespan of a cast-in-place concrete chimney flue is 75 to 100 years.

Signs of Damaged Flue

smoking chimney

Several signs indicate a flue is damaged and needs to be repaired or replaced. These include:

  • Smoke coming into the house from the fireplace
  • A drafty fireplace
  • Soot on the surrounding walls or ceiling
  • Cracks in the chimney structure

When a flue is damaged, carbon monoxide can leak into your home. This can be a severe health hazard, especially if children or older people live in the home.

Some of the risks of carbon monoxide are colorless and odorless, so you may not know that it’s present. It can also be deadly at high concentrations. Symptoms of carbon monoxide poisoning include headache, dizziness, nausea, and confusion.

Carbon monoxide is hazardous because it is produced by burning fossil fuels such as natural gas, propane, gasoline, and oil. These are all common fuels that we use in our everyday lives. 

That means that we need to be extra careful to ensure that our appliances are vented properly and have working carbon monoxide detectors in our homes.

A broken flue can also cause safety issues for you and your family. If you have young children, they could easily fall into the fireplace if the damper is left open.

Some of the risks of having a broken flue include:

  • Smoke and toxic fumes entering your home
  • A fire in the chimney
  • A decrease in heating efficiency
  • An increase in your energy bills

It’s essential to regularly inspect your fireplace and flue to ensure they’re in good working condition. By doing this, you can prevent any significant problems from occurring.

If you find that your flue is damaged, it’s best to leave the repair or replacement to a professional. Attempting to fix it yourself could put you at risk of further damage or injury.

Fireplace Damper

What Is a Fireplace Damper?

A fireplace damper is a metal plate that sits at the top of the firebox and seals off the flue when the fireplace is not in use. Dampers come in various shapes and sizes, but most are rectangular and fit snugly inside the firebox.

Dampers are opened and closed with a handle attached to the damper plate. You pull on the handle to open the damper to release it from the catch. For some dampers, this will allow you to swing the plate open. Other dampers have handles that need to be turned to open or close them.

How Does a Chimney Damper Work?

The function of a fireplace damper is to prevent heat from escaping up the chimney when the fireplace is not in use. It’s also used to keep cold air and pests from entering the home through the chimney.

The damper should create a tight seal that prevents any air movement when closed. This helps to improve your home’s heating efficiency and saves you money on your energy bills.

It’s important to note that some dampers are designed for decorative purposes only and don’t provide a seal. These dampers are typically made of cast iron and sit at the top of the firebox without attaching to anything.

If you’re not sure if your damper is functional or not, there’s an easy way to test it. Light a candle and hold it near the edge of the firebox. If the flame flickers, there’s a good chance air is coming through the damper.

Do All Fireplaces Have a Damper?

Most fireplaces do have a damper, but some don’t. For example, many gas fireplaces don’t have a damper because they’re designed to be used with the flue open. This allows the hot air to vent directly out of the home and prevents back-drafting issues.

You can still add one if your fireplace doesn’t have a damper. There are a variety of aftermarket dampers available that can be installed relatively easily. However, it’s always best to check with a professional before changing your fireplace.

Types of Fireplace Dampers

Fireplace throat dampers – This type of damper is located just above the firebox and is operated by a lever or knob.

  • Top-mounted damper – As the name suggests, this type of damper is mounted on the top of the chimney. It’s opened and closed with a handle attached to the damper plate.
  • Ball-and-socket dampers – This type of damper has a ball that fits into a socket. The ball is connected to a rod, which is used to open and close the damper.
  • Chain-operated dampers – As the name suggests, this type of damper is operated by a chain. The other end of the chain is typically attached to a knob or lever near the firebox.
  • Throat dampers are located just above the firebox and are operated by a lever or knob. 

Signs of Damaged Flue

If your flue is damaged, it’s essential to get it repaired as soon as possible. Otherwise, you could be at risk of carbon monoxide poisoning or a house fire. There are a few signs that you can look for to determine if your flue needs to be repaired:

  • Efflorescence – This is a white, powdery substance found outside your chimney. It’s caused by water vapor passing through bricks and mortar, which dissolves the minerals in the masonry.
  • Cracks – If you see any cracks in your chimney, it’s essential to get them repaired as soon as possible. Depending on the size and location of the cracks, they could cause serious problems.
  • Missing mortar – If you see any missing mortar, it’s essential to have it repaired as soon as possible. Otherwise, your chimney could become structurally unsound.
  • Leaks – If you notice any leaks around your chimney, it’s essential to get them fixed as soon as possible. Leaks can cause severe damage to your home and even fire.

If you notice any of these signs, it’s best to contact a professional for further fireplace inspection. They’ll be able to tell you if the damage is severe enough that repair or replacement is necessary.

The risks of having a broken damper include:

  • Carbon monoxide poisoning
  • House fires
  • Reduced heating efficiency
  • Higher energy bills.

Fireplace Damper Open Or Closed

How Do You Tell a Damper is Open or Closed?

  1. The easiest way to tell if your fireplace damper is open or closed is to look it up. If you can see the metal flap that covers the opening of your chimney, then the damper is open.
  2. If the metal flap is not visible, the damper might be closed. However, just because you cannot see the metal flap does not necessarily mean that the damper is completely closed. A small crack in the damper could allow air to flow through.
  3. To test whether or not your fireplace damper is entirely closed, hold a piece of paper up to the opening of your fireplace. If you feel a draft coming through, there is still an opening somewhere, and your damper is not entirely closed.
  4. Another way is to check the current position of the damper’s controls. The damper is open if the controls are in the “open” position, the damper is open. Suppose the controls are in the “closed” position.
  5. However, just as before, there could be a small crack that allows air to flow through even when the controls are in the “closed” position. The only way to ensure that your fireplace damper is completely closed is to have it inspected by a professional.

When to Close Fireplace Damper

  1. When the fire and embers have all died out, you should shut the damper on your fireplace to keep warm air from leaking out of the chimney. This prevents heated air from leaving your home through the chimney. Before starting a fire, open and close the damper.
  2. Doing this will help to ensure that the fire burns evenly and efficiently. If you forget to open the damper before lighting a fire, the room can quickly fill with smoke.
  3. If you have a gas fireplace, it is crucial to close the damper when the fireplace is not in use. This prevents cold air from coming into your home through the chimney and prevents animals from entering your home.
  4. It is also vital to close the damper when high winds are outside. High winds can cause dangerous downdrafts that can send flames and smoke back into your home through the fireplace. By closing the damper, you prevent this from happening.
  5. You should also close the damper if you are away from home for an extended period. This will prevent animals and pests from entering your home through the chimney. It will also help keep your home more energy-efficient by preventing warm air from escaping.

When to Open Fireplace Damper

The damper should be open when you are using the fireplace. This allows smoke and combustion gases to escape up the chimney and out of your home.

If the damper is closed, these gases can build up in your home and cause health problems for you and your family.

It is also essential to open the damper when ventilating your home. This will help to prevent mold and mildew from growing in your home.

Mold and mildew need moisture to grow, so by ventilating your home, you prevent them from having a moist environment to thrive.

You should also open the damper if a fire in your fireplace is not burning correctly. This will help to improve the draft and allow more oxygen to reach the fire.

This will help to make the fire burn more evenly and efficiently. If you have a gas fireplace, you should also open the damper if there is an issue with the pilot light.

Opening the damper will help to increase the airflow and make it easier for the pilot light to stay lit.

As you can see, there are many times when it is crucial to open or close your fireplace damper. Knowing when to do this can keep your home safe and comfortable.

Why It’s Important to Close Your Damper in the Summer

You might not think about your fireplace or chimney when the weather is warm. However, it is still essential to close the damper on your fireplace.

If you leave the damper open, hot air outside can enter your home through the chimney. This can make your home very uncomfortable and cause your energy bills to increase.

In addition, if there is a fire in your fireplace that is not entirely extinguished, closing the damper will help prevent sparks and embers from escaping up the chimney and into your attic or roof.

This could start a fire in your home that could be very dangerous for you and your family. So, even though you might not be using your fireplace during the summer, it is still vital to close the damper.

Here are some of the other reasons you should close the damper during summer:

  1. In the summer, a closed damper aids in the retention of cool, air-conditioned air within the home where it belongs.
  2. When you’re not using the fireplace, a shut damper prevents cold air from coming in during the winter.
  3. It helps to reduce your cooling and heating bills.
  4. The smell of creosote and soot can be unpleasant when warmer weather. Closing the fireplace damper will keep these smells out of the house. (An annual chimney cleaning will remove these substances and stop the smell from happening.)
  5. If you lack a chimney cap and your damper is closed, twigs, leaves, rainwater, tiny animals, and other debris will not be able to travel down the chimney and into your house.

What if My Fireplace Doesn’t Have a Damper?

You have a few options if you don’t have a damper or it’s broken, you have a few options. First, you can install a top-sealing damper on the chimney just above the roofline. These are very effective but can be pricey. Another option is to insert an inflatable balloon into the flue. The balloon will block off the flue and prevent heat loss when not in use.

You should never use your fireplace without a damper because it’s incredibly inefficient and unsafe. If you’re not sure whether or not your fireplace has a damper, ask a professional to take a look before lighting any fires.

What Size Fireplace Damper Do I Need?

The size of your fireplace flue will determine the size of the fireplace damper you need. If you have a slight flue, you’ll need a smaller damper. Conversely, if you have a large flue, you’ll need a larger damper.

When choosing a fireplace damper, get one sized appropriately for your fireplace. You don’t need a significant damper if you have a small fireplace. Likewise, you don’t need a small damper if you have a large fireplace.

The type of fireplace you have will also dictate the size of the damper you need. For example, if you have a gas fireplace, you’ll need a different size damper than if you have a wood-burning fireplace.

To determine the size of the fireplace damper, you need to:

  1. Measure the width of your flue and then choose a slightly larger damper. For example, if your flue is 12 inches wide, you’ll want to get a 14-inch damper. This will ensure that the damper fits snugly and doesn’t fall into the fireplace.
  2. Ensure you have the correct size damper. 
  3. Install it yourself or hire a professional to do it for you. 
  4. If you’re not sure how to install a fireplace damper, it’s best to hire a professional


The fireplace damper and flue are essential for safety and efficiency when using a fireplace. Therefore, it is crucial to understand the difference between the two and when to use each one. By following the tips above, you can be sure that you are using your fireplace most safely and efficiently.

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Thomas Green

Thomas has worked in the Chimney & Fireplace field for over 12 years. He is an expert in his trade and loves to help People with their needs. Thomas Write helpful articles so that homeowners can make the most informed decisions about their fireplace and chimney.